The invention concerns a method for the application of lacquer to edges of plates and lists which are used within the furniture industry, and especially of the porous type.
The invention also concerns a system for applying lacquer to the edges of plates and lists which are used within the furniture industry, and especially of the porous type, said system containing one or more application rollers.
With known systems of this type, there have always been problems with the dosing of lacquer on edges of porous materials, such as e.g. MDF plates (MDF=Medium Density Fibreboard) or possibly also chipboards. The greatest problem is that of achieving a lacquer layer of even thickness and of uniform drying. In the application of lacquer to chipboards, the lacquer will penetrate deeper into the core of the board, in that the structure at this point is far more porous than the remaining parts of the board. This accumulation of lacquer in the middle of the board is very inexpedient, in that the lacquer will practically speaking not harden, and thus over a long period of time will emit vapours from the solvents existing in the lacquer. This is not particularly fortunate, especially not if the lacquered boards are used for furniture for e.g. a kitchen or a children""s room.
It has also long been a problem to lacquer edges on several items over a short period of time. One of the methods earlier used as a solution has been to spray the lacquer on the items in a stack. This is difficult to do without the lacquer accumulating in runs or droplets when the edge of the item is not of a homogeneous structure, and therefore neither is a uniform absorption of the lacquer achieved. In making sure that the item has received the necessary amount of lacquer over the whole of the edge, some places will invariably receive too much, which results in the undesirable accumulations of lacquer which must subsequently be machined, e.g. by grinding.
In many cases, this process must be repeated up to several times, which not only makes the lacquering process more costly but also prolongs the processing time.
Another way in which to solve the problem can be as shown in U.S. Pat. No. 4,070,987, which describes an apparatus which lacquers the edges by means of an endless belt, a so-called edge-belt. This method suffers the disadvantages, among other things, that the actual application of the lacquer is not particularly precise, and that a precise application on different profiles can not be achieved without difficulties, in that the method is intended only for applying a top coating of lacquer to pre-processed items.
It is also known to apply lacquer to edge profiles with a system using rollers, whereby edge profiles can be lacquered by means of two corresponding rollers, a dosing roller and an application roller. Here, there is the problem that it is rather expensive to have to change the profile on the application unit, in that the production cost of a set of corresponding rollers for the application of the lacquer is very high. Moreover, these rollers are heavy, which means that it is a slow and often troublesome process to replace them with a set of rollers with another profile.
With the invention, these problems are solved by using the following method with associated system. After pre-processing of the edge, which can involve profile milling and sanding, a layer of lacquer, preferably a highly-viscous acrylic lacquer, is applied to the edge by means of the system according to the invention for the application of lacquer to edge profiles. The lacquer is then hardened using known hardening methods, e.g. by means of ultraviolet light, after which the lacquer is ground and the item/edge is now ready for the top coating or the application of foil by thermal impregnation. In the top coating, use is made of a lacquer with lower viscosity, with which the system can also operate, in that it is possible when necessary to adjust the lacquer transport roller in accordance with the viscosity of the lacquer being used.
The most decisive factor in the application of the lacquer is the actual dosing of the lacquer over the edge profile to be lacquered. With the system according to the invention, a very precise dosing is effected, so that the lacquer can be applied with regard to the differentiated absorption capacity of the surface structure of the work piece. At the same time, the invention also makes it possible for the profile on the application roller and the dosing unit to be changed in an easy, quick and inexpensive manner.
The dosing unit itself consists of a relatively thin plate, which at the one end is shaped approximately the same as the edge profile on the item to be lacquered. The contour of the lacquer dosing unit or CAD reference profile is in some cases identical with the CAD reference profile in the application roller. The lacquer pressure chamber, which at all times when the system is in operation supplies the lacquer dosing unit with lacquer at a constant pressure, together with a horizontal adjustment system, has made it possible to provide the edge with a very accurate dosing of lacquer.
To counter those situations where, for example, an edge profile can be an inclined profile and herewith have a large unfolded surface in the core layer, which will absorb more lacquer than a face layer, the lacquer dosing unit itself can be produced with varying CAD reference dimensions, whereby it is taken into consideration that more lacquer can be applied to the core layer in the above-mentioned situations and with greater item thickness. This will be the case for approximately 50% of the MDF and chipboard edge profiles which are known on the present market.
In addition, it is also possible to change the CAD reference profile in the application roller, or in some cases even change the profile both in the application roller and on the lacquer dosing unit in order to achieve a differentiated lacquer dosing across the profile of the item, for example to apply more lacquer to the core layer of items of greater thickness, and where e.g. an edge profile could have a gradient of approx. 30-45 degrees in relation to the vertical, and herewith have a great unfolded surface in the core layer, with subsequently greater local absorption.
A condition for this precise dosing to be able to be effected is that there is a unit which can deliver the necessary amount of lacquer and the necessary pressure. This is taken care of by a lacquer transport roller. This lacquer transport roller is made up of a number of pressure chambers which ensure that the necessary pressure exists.
The system can be used for the lacquering of edge profiles made of e.g. MDF, HDF (High Density Fibreboard), masonite, chipboard etc. These types are not mentioned as limitations, but because they contain the types of edges which are most difficult to provide with a correct edge lacquering. The system will be able to be used for the lacquering of all normal types of materials which are used for edge profiles.
For items where the face layer and the core layer have more or less the same absorption capacity, the profile of the edge dosing profile is identical with the edge profile groove in the lacquer application roller. The lacquer dosing unit is mounted in sleeves for adjustment in both the horizontal and the vertical direction. This contributes towards ensuring that a uniform and constant amount of lacquer is applied over the edge of the item.
Another advantage of the system of this type is that it takes up very little installation space.
In the event of a possible stoppage of the material supply line, the lacquer application unit automatically moves away from the edge of the item, so that lacquer is not wasted on the surface of the item, and the unit is automatically coupled again when the material supply line is re-started.
In the construction of the system, regard has also been paid to easy cleaning of the lacquer application unit, in that a limited cleaning is adequate providing that it is ensured that the lacquer application part is covered in protection against light.